Half Diallel Analysis and Heat Stress Tolerance Indices for Grain Yield in Bread Wheat

Heterosis and combining ability were determined in bread wheat using 6 x 6 half diallel analysis under normal and late planting dates during seasons 2019/2020 and 2020/2021 at Al-Matana Agricultural Research Station, Agricultural Research Center, Luxor governorate. Mean squares due to genotypes, parents, crosses, general (GCA) and specific combining ability (SCA) were significant or highly significant for the most traits. Days to heading (DH), plant height (PH), spike length (SL) under both dates in addition spikes/plant (NS/P), biological yield/plant (BY/P), harvest index (HI) and 1000 grains weight under normal date and grain yield/plant (GY/P), grains/spike (NG/S) under late date were controlled by additive gene action. The rest traits were controlled by dominance gene action. Under normal date, Sids 14 proved to be a good combiner for NS/P and BY/P. All crosses showed positive highly significant heterobeltiosis for GY/P. The crosses P1XP5 and P3XP4 showed significant or highly significant positive SCA for BY/P, GY/P, number and weight of grains/spike. Under late date, Gemmeiza 11 and Misr 2 proved as good combiner for BY/P, GY/P and NG/S. Significant positive GCA effects found for GY/P of Shandaweel 1. SCA effects were positive significant or highly significant for BY/P and GY/P of the four crosses P1XP3, P1XP5, P2XP6 and P4XP6. The crosses P2XP6, P3XP4, P3XP6 and P4XP6 showed highly significant heterobeltiosis for GY/P. It could be concluded that the two crosses of P1XP5 and P2XP6 were the most heat tolerance with high yield and could be used to obtain segregating populations to apply selection.